A retrograde flow mapping technique that is specific for dopamine-Beta-hydroxylase (DbetaH) containing neurons, has recently been developed. This is based upon the phenomenon of specific uptake and retrograde flow of antibody to DbetaH (ADbetaH) by noradrenergic neurons. Following unilateral injection of ADbetaH into the locus coeruleus (LC), ADbetaH was immunocytochemically visualized within cell bodies of the contralateral LC, and ipsilateral A2 noradrenergic cell groups. Substantial numbers of cells were labelled bilaterally within the A1, A4 and A5 groups. This indicates that noradrenergic fibers arising from distant perikarya may innervate the noradrenergic neurons of the locus coeruleus.